The invention relatmes to a process and device for manufacturing a section, in particular a hollow section, especially from light metal billets, via extrusion in which billets residing in a container are introduced as matrix metal by an extrusion stem into the shape-giving cross-section of a die.
Flat, broad sections are normally extruded from so called rectangular containers having a rounded elongated cross-sectional bore housing a billet of the same shape. A container of this kind with liner enclosed in an outer sleeve is described for example in German Pat. No. 24 17 815.
When extruding light metal the width and height of the container bore are given by the limitation that the ratio of extrusion bore to the cross-sectional area should be larger than 400N/mm.sup.2 and the width about 2.5 times the height. The actual dimensional limits are given by the minimum specific force required to extrude light metal sections.
Some of the disadvantages of such rectangular containers compared with round versions are the higher costs incurred when manufacturing the dummy block, extrusion stem and container bore. Furthermore, as a result of the geometry of the sleeve, elevated stresses arise at the middle of the narrow sides where longitudinal cracks and thus failure of the container can occur, especially when extruding sections of elongated cross-section.
One method for overcoming the problem of longitudinal cracks in rectangular containers is disclosed in U.S. Pat. No. 4,007,619 by Adolf Ames and Alfred Wagner, assigned to the Assignee of the instant invention. In accordance with the '619 patent stresses are reduced in the corners of the narrow sides of the rectangular container by providing an elastic welding material which expands during the pressure stroke of the extruding device so as to aid in reducing cracks. While the foregoing systems offers some advantages over previously known systems, problems still arose in the weld area. Naturally it would be highly desirable to provide a mechanism for extruding wide rectangular hollow sections which does not suffer from the above known disadvantages.
In view of the above, the object of the invention is to enable the manufacture of larger, especially broader extrusion sections without the problems of the conventional rectangular containers, and in addition to increase the possible dimensions of such sections further.